Method for making cellular packaging board with inhibitor

ABSTRACT

A method of making beaded foam molded products with corrosion inhibitor incorporated therein includes the steps of expanding a foamable synthetic resin into puffed beads, spraying onto the puffed beads a liquid containing a vapor phase corrosion inhibitor to provide a coating thereon, and molding the coated puffed beads into a beaded foam molded product with the corrosion inhibitor dispersed throughout the thickness thereof and migratable to the surface thereof.

BACKGROUND OF THE INVENTION

The present invention relates to the manufacture of beaded foam moldedproducts and, more particularly, to an improvement in beaded foam moldedboard and the like which includes a vapor phase corrosion inhibitoruseful in packaging and other applications.

Beaded foam molded products, as used herein, includes board, blocks andforms which are produced by molding expanded beads or prepuffs ofpolystyrene and its interpolymers and its alloys such aspolystyrene/polyethylene, polypropylene and its interpolymers, and suchother resins as may be developed for use in making such board, blocksand forms.

Vapor phase corrosion inhibitor agents presently can be found in stockpackaging materials in several forms such as, for example, inpolyethylene bags, extruded plastic sheeting or film, paperboard andpaper wrapping. Alternatively, such agents can be provided in smallcanisters and other devices containing the inhibitor and permitting itsvapors to emanate therefrom into the package enclosure in which placed.These devices are called emitters in that they emit the vapors of thecorrosion inhibitor over time. In a like manner, such agents may besupplied within paper or fabric packets which are placed in thepackages. Such packets usually take the form of an air permeableenvelope in which is provided a corrosion inhibitor. An example of sucha typical packet is disclosed in U.S. Pat. No. 4,973,448 issued toCarlson, et al. on Nov. 27, 1990. Here it is disclosed to fabricate thepackets or envelopes using fabric material comprised preferably of ansynthetic resin polymer material, such as polyethylene, and a powderedvolatile corrosion inhibitor, such as an organic amine acid salt.

In lieu of such packets and or emitters, solid corrosion inhibitors,e.g. pills or tablets, may simply be placed into the packaging with theshipped item. In some instances, the product being placed in thecontainer may be sprayed or otherwise coated with the corrosioninhibitor. For any of these items to work, the person responsible forpackaging must remember to place the inhibitor into the container or onthe product before shipping. In any event, these approaches involveadded steps and costs and may not be effective for providing protectionfor extended period of time.

Hence, another approach to providing corrosion inhibiting material inpackaging is disclosed in U.S. Pat. No. 5,320,778. In this patent, it isdisclosed to incorporate the corrosion inhibitor in a foam materialduring the extruding process. The corrosion inhibitor used however is avapor phase inhibitor-desiccant composite in which a granular cylocogellis used as the substrate onto which the vapor phase corrosion inhibitingcomponent is deposited and this composite material is incorporated inthe extrusion process.

Beaded foam plank, custom shapes or board and blocks are extensivelyused to provide support for and protect articles being shipped.Frequently, such blocks are configured to provide recesses which seatthe articles, or the beads may be molded into custom shapes. Bagscontaining the corrosion inhibitor are included in packages utilizingsuch beaded foam board to cushion the contents.

In addition, there has been recognized a need to provide inert materialswhich would provide corrosion protection for metal structural elementsin various structures and prior to use in construction.

Accordingly, it is an object of the present invention to provide a novelmethod for making a beaded foam molded product having a vapor phasecorrosion inhibitor incorporated therein and which may be readily usedfor packaging a product which is susceptible to corrosion.

It is also an object of the invention to provide such a method whereinthe corrosion inhibiting material is applied to the puffed foam beads inthe course of the conventional process of manufacture.

Another object of the invention is to provide a novel beaded foam moldedproduct containing a vapor phase corrosion inhibitor throughout.

SUMMARY OF THE INVENTION

It has now been found that the foregoing and related objects may bereadily attained in a method for making beaded foam molded product witha vapor phase corrosion inhibitor incorporated therein which includesexpanding a foamable synthetic resin with a blowing agent into puffedbeads and coating the puffed beads with a liquid containing a vaporphase corrosion inhibitor, The coated beads are transported into ablock, custom mold or plank forming mold, and heat and pressure areapplied to the coated beads in the mold to fuse the beads and form abeaded foam block, custom molded form or plank with the corrosioninhibitor incorporated therethroughout, the inhibitor being able tomigrate to the surface of the molded product and emanate therefrom.

Desirably, the coating step is effected by spraying the liquid onto thepuffed beads as they are being transported from the expanding step tothe mold, preferably as they are passing through a spray chamber. Thisspraying is best effected while the beads are moving upwardly throughthe chamber and the liquid is sprayed upwardly to travel therewith.

Desirably, the liquid is applied in an amount of 4-40 ounces per 100cubic feet of the puffed beads. Preferably, the liquid includes mineraloil or other substance to etch the surface of the beads liquid etchesthe surface of the puffed beads.

Steam is introduced into the mold to fuse the beads into the desiredproduct, and blocks and planks which may be cut into boards of lesserthickness.

The resulting product is a beaded foam molded product board comprisingfused puffed beads coated with a vapor phase corrosion inhibitor whichis dispersed throughout the board and is migratable to the surface ofthe board to emanate therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of a manufacturing installationutilizing a process embodying the method of the present invention;

FIG. 2 is a fragmentary vertical section through the spraying chamber ofthe installation of FIG. 1 showing in detail the process of spraying thepuffed beads;

FIG. 3a is a partially fragmentary perspective view illustrating apackage utilizing a beaded foam packaging insert fabricated inaccordance with the method of the invention;

FIG. 3b is a partially fragmentary perspective view illustrating abeaded foam board fabricated in accordance with the method of theinvention; and

FIGS. 4a and 4b are illustrations of a roofing section beaded foam boardto provide corrosion protection for the metallic fasteners.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning first to FIG. 1, therein schematically illustrated is theapparatus employed in the present invention to create beaded foam blockwhich is then used in packaging or construction applications such asthose illustrated in FIGS. 3a-3c. As illustrated in FIG. 3a, the beadedfoam material of the present invention may be molded or cut to provide arecess 3 in which an article 5 can be securely seated. As illustrated inFIG. 3b, short lengths of board 4' may be cut to provide a liner for thecontainer 1. As will be readily appreciated, the block may be cut intosmall pieces which are used as a filler around articles in a container.Numerous other techniques for the use of beaded foam board are wellknown.

Turning in detail to FIG. 1, foamable synthetic resin and a blowingagent such as pentane are first expanded into cellular beads or puffs inconventional apparatus indicated by the numeral 10. The puffed beads arethen transported into a storage container or hopper 12 wherein they maybe stored for a period of time to allow residual blowing agent toescape. The beds will generally have a diameter of 1/32-1/2 inchdepending upon the resin.

In the next step of the process, the puffed beads are metered out of thestorage hopper 12 by a metering device 14 into a conduit 16 throughwhich they are transported in an air stream effected by the blower 18.In the conduit 16 is an enlarged drum or spray chamber 20 in which theyare sprayed with a liquid composition containing the corrosion inhibitoras they pass therethrough.

The coated beads then continue in the conduit 16 to a storage hopper 22in which they are stored prior to molding into the desired foam. Asrequired, the coated beads are discharged through the conduit 24 into adevice 26 for loading the molds 28 in which they will be fused intoblock, plank or custom shapes in accordance with conventional practicewherein steam introduced into the mold causes them to fuse into the formdefined by the mold. However, other molding processes may also be usedincluding just heat and pressure to fuse the beads.

The resultant molded form has the corrosion inhibitor dispersedthroughout so that it is not only at the surface as formed but canmigrate to the surface from within the thickness of the material.

The puffed beads which are contained in the storage hopper 12 aregenerally kept there for a period of about 12 hours following expansion.Alternatively, the storing of the puffed beads following the expansionstep may be done off-site, with the beads being subsequently loaded intothe hopper 12 when needed just prior to the spraying process. The flowof the beads discharged from the supply means 12 and transported throughthe system is regulated by the metering means 14 is convenientlyregulated between a minimum flow rate of about 30 cubic feet per secondand a maximum flow rate of about 100 cubic feet per second.

Referring now to FIG. 2, therein illustrated in greater detail is thespray chamber 20 which is essentially a diametrically expanded length ofthe conduit means 16 through which the expanded beads or prepuffs aremoved and simultaneously sprayed with the liquid corrosion inhibitor. Asthe beads move from the first section of the conduit means 16 into thechamber 20, the density of the beads greatly decreases due to the changein area of the passage. This is important in accomplishing propercoating of the beads as they move through the chamber 20 because itenable the spray of liquid to pass about and between the otherwiseclosely packed beads. By way of example, in the preferred embodiment thechamber 20 has a length of approximately 4 feet and a diameter rangingbetween 12-14 inches, with the inner diameters of the first and secondsections of the conduit 16 each being about equal to 8 inches, henceconstituting a diameter increase of at about 50 percent.

Disposed within the chamber 20 is a spray head 30 providing a nozzle 32at the center of the chamber 20 and it is upwardly directed in thedirection of the flow of the beads therethrough. The liquid flow to thenozzle 32 is controlled to provide the desired volume for the rate offlow of the beads and it will be appreciated that the liquid spray willmove with the beads as they pass therethrough and into the conduit 16.For most applications, the rate of flow of the liquid is 4 to 30 ouncesof the liquid containing the corrosion inhibitor to 30 to 100 cubic feetof the moving beads.

Once in the storage hopper 22 (which can be replaced by storage bags fortemporary storage), the coated beads may be stored if so desired.Generally the coated beads may be transported to the mold after exitingthe conduit 16; however, storage may increase the etching andpenetration of the beads by the corrosion inhibitor.

FIGS. 4a and 4b illustrate usage of the beaded foam product of thepresent invention in construction application to reduce corrosion of themetallic fasteners. In roofing and other application, moisture tends toproduce corrosion of fasteners or about fasteners, often because ofdeficiencies in the metals which are in contact. These figuresillustrate two roofing applications in which the beam 50 supports metalpurlins (not shown) which provide the basic structure of the roofdecking.

In FIG. 4a, to provide a thermal barrier, fiberglass insulation 52 isprovided over the beams 50 and a thermal block 54 of insulating materialis placed thereon. The clips 56 which secure the purlins to the beam 50are fastened to the beam by the fasteners 58. Use of the beaded foammaterial of the present invention for the thermal block 54 provides adesirable degree of corrosion protection for the fasteners 58.

In FIG. 4b, the beaded foam material of the present invention is used toprovide the thermal block 54d on top of the beam 50 and expandedpolystyrene board 60 is placed thereon.

Various corrosion inhibiting compositions are known for use incombination with organic materials. Generally, such compositions containtriazoles, inorganic and organic nitrites, nitrates, phosphates andcarbonates, and aliphatic and aromatic amines or their salts which arebelieved to migrate to the surface in the presence of water vapor andwhich provide the desired protection although the mechanism is not fullyunderstood. These compositions may also include desiccants and arepreferably water-based compositions which generally include a carriersuch as mineral oil.

Such compositions are described in the literature including Carlson etal U.S. Pat. No. 4,973,448; Miksic et al U.S. Pat. No. 5,139,700; MiksicU.S. Pat. No. 5,209,869; and Miksic et al U.S. Pat. No. 5,320,778.Suitable compositions are readily available from Cortec Corporation ofSt. Paul Minn. and illustrative materials which have been satisfactorilyemployed are those sold by Cortec under the designations VCI-337 andVCI-337F and MASTERBATCH 126.

Generally, the amount of inhibitor required to provide the protectiveproperties is 0.75-2.5 percent by weight of the beaded foam product, andpreferably 1.5-2.0 percent.

Illustrative of the present invention is the following specific example.

In a conventional step, polystyrene and a pentane blowing agent areheated to create expanded puffed beads each having an average diameteron the order of about 0.0625 inch (between 0.6 to 1.2 mm). A volume of50 cubic feet of puffed beads per minute passing through a 14 inchesdiameter spray chamber was sprayed with a liquid corrosion inhibitor atthe rate of 12 ounces per minute. The corrosion inhibitor was that soldby Cortec Corporation of St. Paul, Minn. under the designation VCI-337F.

The coated beads were transported to a hopper from which they weredispensed into a block mold having a width of 50 inches, a depth of 26inches and a length of 18 feet. Following closure of the mold, steam wasintroduced thereinto to effect fusion of the beads into a beaded foamblock.

After removal from the mold, various packaging sections were formedtherefrom and placed in packages with various corrodible articles. Afterstorage for several weeks in a moisture containing atmosphere, thecontainers were opened and the articles stored therein were found to befree from evidence of corrosion.

Thus, it can be seen from the foregoing detailed specification that themethod of the present invention provides a beaded foam material with acorrosion inhibitor incorporated therein which is formed by a highlyefficient process. This beaded foam material can be utilizedconveniently in packaging of various articles to provide both insulationfrom impact and corrosion inhibition, and in building construction toprotect fasteners and other metallic elements from corrosion.

Having thus described the invention, what is claimed is:
 1. A method formaking beaded foam molded products with a vapor phase corrosioninhibitor incorporated therein comprising:(a) expanding a foamablesynthetic resin with a blowing agent into puffed beads; (b) transportingsaid beads through a conduit in suspension in air; (c) coating saidpuffed beads with a liquid containing a vapor phase corrosion inhibitoras they are being transported in suspension in said conduit; (d)depositing said coated beads into a metallic mold; (e) applying heat andpressure to said coated beads in said mold to fuse said beads and form abeaded foam molded product with said corrosion inhibitor incorporatedtherethroughout, said inhibitor being able to migrate to the surface ofsaid product and emanate therefrom; (f) forming said molded product intopackaging inserts; and (g) placing said inserts in an enclosure toprovide a vapor phase inhibitor within said enclosure.
 2. The method ofmaking beaded foam molded product in accordance with claim 1 whereinsaid coating step is effected by spraying the liquid onto the puffedbeads as they are being transported from the expanding step to the mold.3. The method of making beaded foam molded product in accordance withclaim 2 wherein said spraying step is conducted by spraying said liquidonto the beads as they are passing through a spray chamber.
 4. Themethod of making cellular packaging polystyrene board in accordance withclaim 3 wherein said beads are moving upwardly through said chamber andsaid liquid is sprayed upwardly to travel therewith.
 5. The method ofmaking beaded foam molded product in accordance with claim 1 whereinsaid liquid is applied in an amount of 4-40 ounces per 100 cubic feet ofsaid puffed beads.
 6. The method of making beaded foam molded product inaccordance with claim 1 wherein said liquid etches the surface of saidpuffed beads.
 7. The method of making beaded foam molded product inaccordance with claim 1 wherein steam is introduced into said mold tofuse said beads into said molded product.
 8. The method of making beadedfoam molded product in accordance with claim 1 including the step ofcutting said product into smaller sections.
 9. A method for makingbeaded form molded products with a vapor phase corrosion inhibitorincorporated therein comprising:(a) expanding a foamable synthetic resinwith a blowing agent into puffed beads; (b) coating said puffed beadswith a liquid containing a vapor phase corrosion inhibitor by sprayingsaid liquid into said puffed beads in a spray chamber as they are beingtransported from the expanding step to the mold, said beads movingupwardly through said chamber and said liquid being sprayed upwardly totravel therewith; (c) depositing said coated beads into a mold; and (d)applying heat and pressure to said coated beads in said mold to fusesaid beads and form a beaded foam molded product with said corrosioninhibitor incorporated therethroughout, said inhibitor being able tomigrate to the surface of said product and emanate therefrom.
 10. Themethod of making beaded foam molded product in accordance with claim 9wherein said liquid is applied in an amount of 4-40 ounces per 100 cubicfeet of said puffed beads.
 11. The method of making beaded foam moldedproduct in accordance with claim 9 wherein said liquid etches thesurface of said puffed beads.
 12. The method of making beaded foammolded product in accordance with claim 9 including the step of cuttingsaid product into smaller sections.